Circuit boards are major components present in virtually all electrical instrument and electronics. It has completely effected a change in the world for life. However, working with a faulty circuit board is common, even if it is not used for any technical requirement. At one point in time, every engineer has experienced a bad scenario, in which they survived.
Therefore, in order to use your instruments properly, it is very important to learn how to check your circuit board for any fault. Circuit boards are made up of many different components; this is why the board diameter may have some defects.
Though the list seems long, you can check these faults quickly using a multimeter. Therefore, we will be discussing the methods when making use of a digital multimeter to check the PCB for any electrical fault. Let’s consider various methods on how to test a circuit board.
Testing for Faults in Circuit Boards
Below are some vital steps that you can use as a tester for your circuit boards
- Finding short circuits in PCBs
- Testing for short circuits on electronic boards
- Finding faulty components on a printed circuit board
Finding short circuits in PCBs or Faults in Circuit Boards
The multimeter is known as dependable equipment that helps in checking shorts and other electronic faults present in almost every electrical device. Making use of a multimeter circuit board, it is possible to easily inspect it for current, capacitance, input voltage, resistance, AC & DC voltage, fuse shorts, etc.
Due to the fact that it performs many circuit board testing jobs all at once, this tool is usually regarded as the combination of the voltmeter, ammeter, and multimeter.
Before using multimeter probes as a method for finding electronic faults, it is important that you go through other inspection methods. Let’s consider them.
Assume you have passed the stage of breadboard design and a circuit breaker is absent, then the first step that you should take when locating the short circuits present on the PCB is looking carefully at the whole PCB surface.
Furthermore, if there is one available, make use of a microscope of low magnification or a magnifying glass all through the examination to test a circuit board.
Beginning with the power supply, search for tin whiskers present between the solder joints or pads. When you notice any blobs or cracks of solder, it should get your attention. Check the entire vias, if unplated vias is what you specified, then ensure the same holds for the circuit board. Vias that are poorly plated can help in creating short integrated circuits in-between the layers, with everything now tied to VCC, ground, or both.
When the short becomes very bad and leads to components reaching the critical temperatures, then you will see some burned spots present on the circuit board.
In-depth Physical Inspection
An in-depth physical inspection will also give you some practical and useful insights into a malfunctioning circuit board. This is also useful in identifying the faulty components, that normally, you wouldn’t have been able to identify it via visual inspection alone. To get better results, you can make use of an oscilloscope.
Making use of infrared camera will assist you in locating areas where there is large heat generation. Furthermore, if you aren’t seeing hot spots away from the active components, then there is a chance that you have circuit board short circuits, even when this short is between the internal layers.
Usually, the short has higher resistance compared to the solder joint or normal trace. This is because it doesn’t enjoy the benefit of getting optimized in the design. This resistance, coupled with high current that happens naturally as a result of the direct electrical connection that happens between the power and ground, this means that the conductor present in PCB short circuits will end up heating up.
Begin with the lowest possible current. Ideally, you will see this short before the short does more damage.
Testing for short circuits on Electronic Boards
Asides visual inspection, there are other ways by which you can find the major causes of a PCB short circuit.
Circuit Board Testing Making use of a Digital Multimeter
To test a circuit board for short circuits, there is a need for you to check the known resistance present between the different circuit points. However, if your visual inspection fails to reveal clues concerning the cause or location of a short circuit, then get a multimeter and then try tracking down the PCB’s location.
This multimeter approach usually gets different mixed feelings online especially in majority of electronics forums. However, the tracing of the test points of the short circuit can go a long way in revealing the problem.
The multimeter to use here must have milliohm sensitivity. Furthermore, it would be great if it can alert you immediately you start probing shorts. For example, measuring the resistance present between the neighboring pads or traces on a printed circuit board, you have to measure a high resistance.
Finding Ground on Circuit Boards
One important aspect here are short that involves a grounded plane or grounded via. Multilayer PCBs having interior ground planes will have return paths. This offers the best location to inspect and check all the other pads and vias on the board’s surface layer. Set a probe on the ground connection, and then touch the other probes all through the board’s other conductors.
Another thing is that you will also find this ground connection on other board locations. This means that you’ll read an extremely small resistance when each prove is touched to two grounded vias that are different. Be very attentive to the layout when doing this, because you wouldn’t want to make any error for a ground connection.
When you are checking for shorted or faulty components, this means that you are making use of the multimeter in measuring the resistance. For cases whereby the visual inspection doesn’t reveal excess metallic flakes or solder between the pads, then the forming of the short may have been done in the internal layers between the two pins/pads on a component.
Furthermore, shorts can also occur as a result of poor fabrication; one reason why printed circuit boards have to undergo design rule checks and DFM. Vias and pads placed near each other could short unintentionally or bridge during fabrication
For this case, you will have to measure that resistance present between the pins present on a connector or an IC. Also, pins close together are usually prone to shorts. However, shorts can still form in other locations. Check to ensure that there is a low resistance present between the pins/pads with themselves and to the ground connection.
Narrow the Location Down
Once you feel you’ve located shorts between the two conductors or in-between the ground and some conductor, then you should narrow the location down by looking into the nearby conductors.
Finding Faulty Components on a Printed Circuit Board
Faulty components of components installed incorrectly could cause some problems in the board. These components could either be a counterfeit or is faulty. This creates shorts and on appearance of one.
It is possible for some components to suddenly gob bad. An example of this is the electrolytic capacitor. If there is any component you suspect, check it first. Now, if you are not sure you can do a Google search for the component you suspect has failed. Also, try to know if the issue is a common one.
For cases, whereby you measure an extremely low resistance present between the two pins/pads, you may end up having a short circuit as a resuly of the component that has burned out. This sign clearly indicates that the capacitor is bad. Also, capacitors bulge when they are bad or one the voltage applies passes the required amount.
What you should do with a Faulty Circuit Board?
Using a faulty circuit board or faulty pcb could be hazardous for different electronics devices. Therefore, you may have to either replace this damaged or faulty circuit board or repair. This is mainly to prevent hazards from these damaged parts according to the EPA.
Therefore, it is highly recommended that you work with a professional electrician to assist you wit replacing the copper traces or the circuit with shorts. This ensures that the unit functions properly.
Any printed circuit board is usually manufactured in smaller copper traces. Also precision is used during the connection. Therefore, even a very slight defect can ruin the entire device. This is one reason why for the safety of the user as well as ensuring that the electrical devices performs for lone, you must learn how best to check these integrated circuits for faults. If you successfully identify the malfunctioning, you may either resolve it yourself quickly or ask an expert to help you out.